In the industry, variability of cement reaction temperature results in variability in injection and delivery characteristics. Many low compliance injectors like the 1 cc syringe and other commercially available injectors may increase radiation exposure to the operator.
Bone cement temperature can vary considerably and therefore its handling characteristics can vary. Currently available injectors may have low compliance but forces operator to remain close to the radiation source, for example an x-ray beam, wherein other injectors have lesser compliance but allow further distance from the x-ray beam.
Others have attempted to solve the problem by using water baths to adjust the temperature of the cement, freezing the cement in the injector, adjusting the temperature of the orthopedic appliances being placed at surgery, adjusting the cement polymerization time by changing its components, and constructing the injector out of low-compliance materials. All of these attempts have failed to solve the current problems.
U.S. Pat. No. 6,264,659 to Ross et al. describes the use of heat only with no possibility or need for cooling. In Ross et al. the reaction is a phase change in the thermoplastic material rather than a polymerization reaction which changes the chemicals irreversibly. Applicant uses thermal elements to control the rate of a chemical reaction. In Ross et al. there is no need for the operator of the device to be a certain distance from the patient (no radiation), as distance from the patient is not an issue, it is better for the operator to be closer to the patient so that the material does not set before entering the disc.
U.S. Pat. No. 5,324,305 to Kanner describes the use of a thermoplastic heater with a solid bio adhesive which flows when heated, and is used to treat the eyes. The bio adhesive is a solid at room temperature, and must be “melted” for application and operates like a glue gun.
U.S. Publication No. 2005/0245938 to Kochan describes a detachable balloon filled with the thermoplastic material in addition to heating a thermoplastic elastomer to treat intervertebral discs or articular joint spaces.
U.S. Publication No. 2006/0122625 to Truckai et al. describes changing the temperature of the bone cement by radiofrequency energy generated heat, and in some embodiments not confined to the tip of the probe but also occurring within the tissue. Truckai et al. also alludes to using other energy forms to heat the cement, such as laser, ultrasound, etc., but does not disclose cooling or heating or using other chemical agents to create hot or cool temperatures. Truckai et al. focuses primarily on heating to accelerate the cement polymerization process. Applicant uses cooling and heating together serially or individually to speed or slow the reaction of the cement.
In addition to the above, greater control of cement delivery through mechanical (elongated small barrel syringe) and/or thermal jacket, control of polymerization, and increased radiation safety by maintaining distance from the x-ray beam is needed in the industry.
Advantages of some embodiments of the present invention may include, in part, but are not limited to, less compliance of injector; 1:1 control when pushing or pulling on syringe; reduced movement of connecting and unconnecting syringe to needle; total volume for each injection is in its own syringe; two syringes for two needle procedure, reduced radiation exposure for operator and patient, altering the working time and viscosity of the bone cement by altering the temperature of the thermal jacket, use with different cement formulations which inherently set up faster or slower; and accelerating or slowing the cement polymerization reaction, and use of two injectors for two needle procedures facilitating delivery and use of radiation shields. Commonly this would be useful in treating spinal fractures, as with vertebroplasty or kyphoplasty.